Method of producing electrical contacts



Jan. 28, 1930. J. SHALLCROSS 1,744,810

METHOD OF PRODUCING ELECTRICAL CONTACTS Fi led June 22, 1927 f/yz.

f/qi //5 J5 k 2 a w Mme/War flmes Ska/crass WW My Patented Jan. 28, 1930' UNITED STATES PATENT OFFICE JAMES SHALLCROSS, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK METHOD OF PRODUCING ELECTRICAL CONTACTS Application filed June 22,

This invention relates to a method of producing electrical-contacts, and more particularly to a method of providing electrical relay or switch springs with contact points.

The contact points of relays and switches such as those used in telephone apparatus where the circuit is frequently interrupted are exposed to the oxidizing and corrosive efiects of the heat generated by the are when the circuit is broken and for this reason the contact points are commonly made of a highly refractory metal such as platinum or an alloy. Heretofore, it has been the practice to weld to the contact spring a contact point of platinum or other contact metal exhibiting the desired properties of a size suflicient to give the desired height, contact surface and configuration, the latter being obtained by subjecting the contact metal to a swaging operation. However, such a method requires a considerable amount of contact metal which is quite expensive which makes it highly desirable to use as little of this metal as possible.

An object of the present invention is to provide a simple and efficient method of producing electrical contacts with a minimum amount of contact metal.

The invention contemplates the provision of a method of producing an embossed contact capped with a suitable contact metal. In accordance with one embodiment of the invention a small piece of contact metal is welded to the member to be provided with a contact after which the contact metal and a portion of the member are formed into a contact point in a single operation.

It is believed that a complete understanding of the invention may be had by reference to the following description, taken in conjunction with the accompanying drawing, in which Fig. 1 diagrammatically illustrates the operation of welding the contact metal to a contact spring;

Fig. 2 shows the welded contact metal severed from the supply rod;

Fig. 3 shows the member and the contact metal just prior to the embossing operation, and

' Fig. 4: shows the completed contact point.

1927. Serial No. 200,553.

Referring to the drawings in which similar reference numerals indicate the same parts in the several views, the numeral 6 indicates the end portion of a contact spring of any suitable type to be provided with a contact point. The spring may be made of a nickelsi lver alloy, and a contact metal, such as platinum, in the form of a rod 7 is fed to the spring through a holder 8. lVhen the rod 7 of contact metal is in contact with the spring 6, a current from a source 9 is applied through the holder 8 which also serves as an electrode, and a second electrode 11 to firmly weld the rod to the spring. The rod is then severed leaving a small projection 12 of the contact metal welded to the spring, as shown in Fig. 2. The spring with the projection of contact metal is then placed on a tool 13 having a boss 14 in such a position that the projection 12 is directly opposite the boss as shown in Fig. 3 and a swaging tool 15 provided with a cavity 16 in alignment with the boss 14 and having the shape of the contact point to be formed, is caused by any suitable means such as a press (not shown), to strike the spring forcing the small projection of contact metal 19. into the cavity and filling the remainder of the cavity with spring metal as shown in Fig. l, thus forming a cap of the contact metal over that portion of the embossed part of the spring which is exposed to the effects of the arc. In this manner the contact metal in the projection and also the metal of the spring entering into the contact point are formed in a single operation, which greatly simplifies the production of contact springs in large numbers. Also, the required height of contact surface and configuration are obtained by the use of a minimum amount of contact metal which materially decreases the cost of the contact springs.

It will be understood that the embodiment of the invention herein described and illustrated is merely a convenient and useful form of the invention which is capable of other modifications without departing from the spirit and scope of the invention.

lVhat is claimed is:

1. A method of producing an electrical contact on a contact member, which consists of welding a portion of contactmetal on the member, and forming the contact metal and a portion of the member into an electrical contact projecting from the member and having a portion thereof covered with contact metal.

2. A method of producing a contact point on a contact member, which consists of welding the end of a rod of contact metal to the member, severing a portion of the rod so as to leave a projection of contact metal attached to the member, and forming the contact metal and a portion of the member into a contact point.

3. A method of producing a contact point on a contact member, which consists of attaching a portion of contact metal to the member and simultaneously forming the contact metal and a portion of the contact member into a contact point integral with and extending from the member and having contact metal covering the top and a portion of the side thereof.

4. A method of producing a contact point on a contact member, which consists of engaging a rod of contact metal with the member, welding the end of the rod to the member, severing a portion of the rod leaving it attached to the member, and forming the contact metal and a portion of the member into a contact point.

5. A method of producing a contact point on a contact member, which consists of welding a portion of contact metal on the member and simultaneously forming an embosse portion on the member and capping the area of the embossed portion which is exposed to the arc with the contact metal.

6. A method of producing a contact point on a contact member, which consists in weld- 40 ing a portion of a contact metal on the member, and simultaneously embossing the portion of the contact member which lies directly beneath the portion of contact metal and shaping the contact metal to cap the top of the embossed portion of the contact member.

In witness whereof, I hereunto subscribe my name this 11th day of June A. D., 1927.

- JAMES SHALLCROSS. 

